Formation method for preparing a fast-charging lithium ion cell

ABSTRACT

Methods, systems and battery modules are provided, which increase the cycling lifetime of fast charging lithium ion batteries. During the formation process, the charging currents are adjusted to optimize the cell formation, possibly according to the characteristics of the formation process itself, and discharge extents are partial and optimized as well, as is the overall structure of the formation process. During operation, voltage ranges are initially set to be narrow, and are broadened upon battery deterioration to maximize the overall lifetime. Current adjustments are applied in operation as well, with respect to the deteriorating capacity of the battery. Various formation and operation strategies are disclosed, as basis for specific optimizations.

CROSS REFERENCE TO RELATED APPLICATIONS

This application in a continuation-in-part of U.S. patent applicationSer. No. 15/867,764, filed on Jan. 11, 2018, which claims the benefit ofU.S. Provisional Patent Application No. 62/445,299 filed on Jan. 12,2017, all of which are incorporated herein by reference in theirentirety.

BACKGROUND OF THE INVENTION 1. Technical Field

The present invention relates to the field of lithium ion batteries, andmore particularly, to formation processes and operation patterns whichincrease the cycling lifetime of fast-charging lithium ion batteries.

2. Discussion of Related Art

Lithium ion batteries are typically used as energy storage devices forsupplying power for various devices and appliances, and operate bylithiation of lithium ions from the electrolyte into the anode material(intercalation in case of graphite anodes), wherein in initial chargingand discharging cycles, a SEI (solid-electrolyte interphase) layer isformed by interaction between electrolyte components and Li ions on theanode surface, and supports proper later operation of the cells in termsof cell capacity, cycle life and degradation mechanism.

SUMMARY OF THE INVENTION

The following is a simplified summary providing an initial understandingof the invention. The summary does not necessarily identify key elementsnor limit the scope of the invention, but merely serves as anintroduction to the following description.

One aspect of the present invention provides a method of preparing afast-charging lithium ion cell for use by forming a solid-electrolyteinterphase (SEI) in the anode, the method comprising: performing a firstcycle of fully charging the cell and consecutively discharging the cell,and performing, consecutively, a plurality of charge-discharge cycles,in which the cell is charged and discharged to any value between 30-80%(or between 20%-80% or between 10%-90%) of maximal cell capacity in eachof the cycles.

These, additional, and/or other aspects and/or advantages of the presentinvention are set forth in the detailed description which follows;possibly inferable from the detailed description; and/or learnable bypractice of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of embodiments of the invention and to showhow the same may be carried into effect, reference will now be made,purely by way of example, to the accompanying drawings in which likenumerals designate corresponding elements or sections throughout.

In the accompanying drawings:

FIGS. 1-3 are high-level schematic illustrations of systems and methodsfor increasing the cycle life of fast-charging lithium ion batteries,according to some embodiments of the invention.

FIGS. 4 and 5 provide non-limiting examples for formation processes,according to some embodiments of the invention.

FIG. 6 provides a non-limiting example that illustrates, according tosome embodiments of the invention, the additional improvement in cyclelifetime when using current adjustments in the first cycle with respectto using a constant charging current.

FIG. 7 is a non-limiting example of two formation processes, accordingto some embodiments of the invention.

FIG. 8 is a high-level schematic illustration of the fast-charginglithium ion cell, being charged in a SEI formation process,characterized by the cell cycling configurations, according to someembodiments of the invention.

FIGS. 9-11 are high-level schematic illustrations of operating afast-charging lithium ion battery, according to some embodiments of theinvention.

FIG. 12 is a high-level schematic illustration of controlling theparameters for operating a fast-charging lithium ion battery unit orbattery in multiple voltage ranges, according to some embodiments of theinvention.

FIG. 13 is a high-level schematic illustration of operating afast-charging lithium ion battery unit or battery in multiple voltageranges, according to some embodiments of the invention.

FIGS. 14A and 14B demonstrate results that indicate the improvedperformance of fast charging batteries when operated according to thedisclosed scheme, according to some embodiments of the invention.

FIG. 15 provides a non-limiting example for the increased cycle lifetimeof the battery operated with adjusted charging currents according to thedeteriorating capacity of the battery, according to some embodiments ofthe invention.

FIGS. 16A-C provide examples for current adjustments corresponding tocell deterioration, according to some embodiments of the invention.

FIG. 17 provides a non-limiting example for current ramping at thebeginning of charging during battery operation, according to someembodiments of the invention.

FIG. 18A illustrates the cell temperature during cycling with currentadjustments, according to some embodiments of the invention, compared toFIG. 18B illustrating the cell temperature during cycling with constantvalues for the charging currents.

FIG. 19 is a high-level schematic illustration of various anodeconfigurations, according to some embodiments of the invention.

FIGS. 20A-C provide a schematic model for lithiation and de-lithiationof the anode material particles during operation of the battery,according to some embodiments of the invention.

DETAILED DESCRIPTION OF THE INVENTION

In the following description, various aspects of the present inventionare described. For purposes of explanation, specific configurations anddetails are set forth in order to provide a thorough understanding ofthe present invention. However, it will also be apparent to one skilledin the art that the present invention may be practiced without thespecific details presented herein. Furthermore, well known features mayhave been omitted or simplified in order not to obscure the presentinvention. With specific reference to the drawings, it is stressed thatthe particulars shown are by way of example and for purposes ofillustrative discussion of the present invention only, and are presentedin the cause of providing what is believed to be the most useful andreadily understood description of the principles and conceptual aspectsof the invention. In this regard, no attempt is made to show structuraldetails of the invention in more detail than is necessary for afundamental understanding of the invention, the description taken withthe drawings making apparent to those skilled in the art how the severalforms of the invention may be embodied in practice.

Before at least one embodiment of the invention is explained in detail,it is to be understood that the invention is not limited in itsapplication to the details of construction and the arrangement of thecomponents set forth in the following description or illustrated in thedrawings. The invention is applicable to other embodiments that may bepracticed or carried out in various ways as well as to combinations ofthe disclosed embodiments. Also, it is to be understood that thephraseology and terminology employed herein is for the purpose ofdescription and should not be regarded as limiting.

Unless specifically stated otherwise, as apparent from the followingdiscussions, it is appreciated that throughout the specificationdiscussions utilizing terms such as “processing”, “computing”,“calculating”, “determining”, “enhancing” or the like, refer to theaction and/or processes of a computer or computing system, or similarelectronic computing device, that manipulates and/or transforms datarepresented as physical, such as electronic, quantities within thecomputing system's registers and/or memories into other data similarlyrepresented as physical quantities within the computing system'smemories, registers or other such information storage, transmission ordisplay devices. Any of the disclosed modules or units may be at leastpartially implemented by a computer processor.

Embodiments of the present invention provide efficient and economicalmethods and mechanism for preparing lithium ion cells for prolongedoperation, particularly under fast charging scenarios, by forming astable SEI, and thereby provide improvements to the technological fieldof fast charging batteries.

Methods, systems and battery modules are provided, which increase thecycling lifetime of fast charging lithium ion batteries. During theformation process, the charging currents are adjusted to optimize thecell formation, possibly according to the characteristics of theformation process itself, and discharge extents are partial andoptimized as well, as is the overall structure of the formation process.During operation, voltage ranges are initially set to be narrow, and arebroadened upon battery deterioration to maximize the overall lifetime.Current adjustments are applied in operation as well, with respect tothe deteriorating capacity of the battery. Various formation andoperation strategies are disclosed, as basis for specific optimizations.

Cells and methods are provided, which improve the SEI (solid-electrolyteinterface) formation process and provide fast-charging lithium ion cellswith prolonged lifetime due to increased SEI stability. SEI formationmethods are characterized by partial charging and/or discharging in atleast some of the SEI formation cycles, for example full charging anddischarging in a first cycle followed by partial charging anddischarging in consecutive cycles; or partial charging and dischargingin a first cycle followed by partial charging and discharging inconsecutive cycles. SEI formation methods may comprise using lowcurrents.

Disclosed embodiments relate mainly to fast charging batteries, whichare characterized by high charging and/or discharging rates (C-rate),ranging from 3-10 C-rate, 10-100 C-rate or even above 100 C, e.g., 5 C,10 C, 15 C, 30 C, 100 C or more. It is noted that the term C-rate is ameasure of the rate of charging and/or discharging of cell/batterycapacity, e.g., with 1 C denoting charging and/or discharging the cellin an hour, and XC (e.g., 5 C, 10 C, 50 C etc.) denoting charging and/ordischarging the cell in 1/X of an hour—with respect to a given capacityof the cell. In certain embodiments, the terms charging currents andC-rates are used interchangeably in a non-limiting manner, relating togiven cell capacities and/or cell capacities determined as disclosed.

The inventors have found out that the lifetime of fast-charging lithiumion batteries may be extended by delivering power from the batterieswithin a narrow voltages range when the battery is relatively fresh andhas high capacity, and broadening the voltages range only once theresistance of the battery increases and its capacity decreases. Thisoperation scheme is contrary and superior to prior art operation oflithium batteries within the full voltages range from the start. Theinventors have found out that disclosed operation schemes increase thelifetime of the fast-charging lithium ion batteries.

Fast-charging lithium ion batteries, charging management modules andmethods are provided, which modify the range of voltage levels suppliedby the battery according to a state of health of the battery, startingfrom a narrow range and reaching a wider range—to maximize the batterylifetime. The range of supplied voltage levels may be determinedaccording to the resistance of the battery to minimize the loss ofcapacity of the battery and thereby increase its lifetime.

Embodiments of the present invention provide efficient and economicalmethods and mechanisms for improving battery performance by controllingits output voltage levels and thereby provide improvements to thetechnological field of fast-charging lithium ion batteries.

In certain embodiments, fast-charging lithium ion batteries may compriseany number of cells, having respective anode(s), cathode(s),separator(s) and electrolyte(s) made of any of a variety of materials.For example, anodes may be made of anode material in form of anodematerial particles (e.g., having a diameter of 100-500 nm), which maycomprise e.g., particles of metalloids such as silicon, germanium and/ortin, and/or possibly particles of lithium titanate (LTO), possiblyparticles of aluminum, lead and/or zinc, and may further include variousparticle surface elements (e.g., having a diameter of 10-50 nm or less)such nanoparticles (e.g., B₄C, WC, VC, TiN), borate and/or phosphatesalt(s) and/or nanocrystals and possibly polymer coatings (e.g.,conductive polymers, lithium polymers). Anode(s) may be made from anodeslurry prepared by ball milling processes and may further compriseadditive(s) such as binder(s), plasticizer(s) and/or conductivefiller(s). In certain embodiments, anode(s) may be graphite orgraphene-based. Cathode(s) may comprise materials based on layered,spinel and/or olivine frameworks, and comprise various compositions,such as LCO formulations (based on LiCoO₂), NMC formulations (based onlithium nickel-manganese-cobalt), NCA formulations (based on lithiumnickel cobalt aluminum oxides), LMO formulations (based on LiMn₂O₄), LMNformulations (based on lithium manganese-nickel oxides) LFP formulations(based on LiFePO₄), lithium rich cathodes, and/or combinations thereof.Separator(s) may comprise various materials, such as polyethylene (PE),polypropylene (PP) or other appropriate materials. Electrolyte(s) maycomprise any of a wide range of corresponding fluids, such ascarbonate-based cyclic and linear compounds provided below.

FIGS. 1, 2 and 3 are high-level schematic illustrations of systems 401and methods 400 for increasing the cycle life of fast-charging lithiumion batteries, according to some embodiments of the invention.

FIG. 1 is a high-level schematic block diagram illustrating batteryformation and operation systems 401, according to some embodiments ofthe invention. Formation processes 200, which are typically carried outat the battery production factory, and operation processes 300, whichare typically carried out by the users of batteries 90, are configuredand optimized in disclosed embodiments primarily to increase the cyclelife of batteries 90, namely the number of charging and dischargingcycles battery 90 can go through before reaching a predefineddeterioration of its performance (e.g., capacity reaching 80% of anoriginal capacity, or a specified value). During formation 200, acharge/discharge system 100 controlled by controller 105 as a chargingmanagement module, is configured to carry out formation cycles 120comprising multiple charging and discharging steps of battery 90,typically characterized as a first cycle 120A and consecutive cycles120B. Examples for cycle characteristics which may be determined bycontroller 105 are the end of charging (C-end) criterion 101 (an example101A denoted on the schematic formation curve) and the extent ofcharging (maximal capacity or voltage) and discharging (depth ofdischarge DoD), denoted schematically by numeral 101B. Certainembodiments disclosed below provide ways of defining these criteria tooptimize the formation process, e.g., my initially measuring lithiationcapacities of the anodes and cathodes in half cells 91 and using themeasured quantities to define formation criteria 101A, 101B, as well asoptionally providing feedback 106 from formation curve 120 of battery 90to modify formation criteria 101A, 101B during formation 200 itself, oras a way to derive formation parameters for formation processes 200 ofbatteries that follow. During operation 300, a controller 135 such as abattery management system (BMS) which may be at least partly integratedwith battery 90 determines charging and/or discharging windows 141 ofbattery 90 in the device, depending on its use. Charging and/ordischarging windows 141 determine an operation curve 141A of battery 90,which in disclosed embodiments, typically starts with narrow voltagerange window cycling 140 and the voltage range window is graduallyincreased (140A . . . N) as battery 90 deteriorates, up to a maximalvoltage range 145 in which the battery is operable (and which is theprior art default operation voltage range). Optionally feedback 137A maybe provided to controller 135 to optimize the modifications in chargingwindows. Parameters derived from formation process 200 may be used incontrolling the cycles of operation process 300, as disclosed below.

As illustrated schematically in FIGS. 2 and 3, method 400 may compriseconducting a formation process of the battery (stage 200) and operatingthe battery (stage 300) according to embodiments of the invention—toextend a cycling life time of the fast charging lithium ion battery.

Methods 400 may comprise conducting formation process 200 of the batteryby performing a first cycle of fully charging the battery at a rate ofless than C/30 and consecutively discharging the battery (stage 240),and, consecutively, performing a plurality of charge-discharge cyclese.g., at C/10 or more, e.g., C/5 (stage 245). In various embodiments,the first cycle may be carried out at e.g., 0.1 C, 0.03 C, 0.01 C orvalues in-between, and consecutive cycles may be carried out at 0.2 C,0.1 C, 0.05 C, possibly higher values such as 0.5 C or even 1 C, orvalues in-between. In certain embodiments, first cycle may be carriedout at a variable rate, starting e.g., from 0.1 C, 0.03 C, 0.02 C, 0.01C or values in-between and increasing (e.g., step-wise and/or gradually)during the first cycle to e.g., 0.2 C, 0.3 C, 0.5 C, possibly to highervalues such as 1 C or values in-between, until the end of the firstcycle.

In formation process 200, method 400 may further comprise determining,prior to the first cycle, a cell capacity as the lower between a firstlithiation capacity of the anode and a first delithiation capacity ofthe cathode (stage 410)—measured in a half cell with respect to lithium(stage 405), and terminating the full charging in the first cycle uponreaching the determined cell capacity (C) as a criterion for ending thecharging in the first cycle (stage 410). For example, the cell capacitymay be defined as indicated in Equations 1:C ₀ (mAh)=Min (Cathode material mass inside the cell·C _(c), Anodematerial mass inside the cell·C _(a)), with:C _(c) (mAh/gr)=1^(st) delithiation capacity of cathode vs. Li metal inthe half cellC _(a) (mAh/gr)=1^(st) lithiation capacity of anode vs. Li metal in thehalf cell   Equations 1

In a non-limiting example, the first formation cycle may be carried outat C₀/30 rate to full charge, followed by discharge, and consecutivecycles may be four or more at C₁/10 rate with C₁ being the dischargecapacity measured or estimated after the first cycle. Method 400 maycomprise increasing the number of consecutive formation cycles (stage420), found out by the inventors to improve lifetime of the formedbattery.

In certain embodiments of formation process 200, method 400 may furthercomprise terminating the charging in the plurality of charge-dischargecycles upon reaching the determined cell capacity, or a specifiedpercentage thereof (stage 425)—as illustrated schematically by numeral101A in FIG. 1, which correspond to a charging-end criterion 101 such asreaching the determined cell capacity, or a specified percentagethereof. In certain embodiments of formation process 200, method 400 mayfurther comprise adjusting the cell capacity according to dischargecapacities determined at each cycle, and terminating the charging ineach cycle accordingly (stage 427). In either case, adjustingcharging-end criterion 101 (at any of formation stages 120 such as firstor consecutive cycles 120A, 120B, respectively) may be configured tooptimize the efficiency and duration of the formation process.

In a non-limiting example, the first formation cycle may be carried outat C₀/30 rate to full charge, followed by four or more cycles at C₁/10rate with C₁ being the discharge capacity measured or estimated afterthe first cycle. Method 400 may comprise increasing the number ofconsecutive formation cycles (stage 420), e.g., to four charge-dischargecycles or more, which was found by the inventors to improve lifetime ofthe formed battery. FIG. 4 provides a non-limiting example for formationprocess 200, according to some embodiments of the invention. FIG. 4illustrates CC-CV (constant current-constant voltage) first andconsecutive formation cycles 120A, 120B, respectively, with fourconsecutive formation cycles 120B. This non-limiting example forformation and operation resulted in improved cell lifetime with respectto prior art formation without the limitation of cell capacity and withless than four, typically one or two consecutive formation cycles, yetthe formation process is quite time consuming, taking ca. 120 hours.

In certain embodiments of formation process 200, method 400 may furthercomprise adjusting the current of the charging stage of the first cycleduring charging (stage 430) according to any of a variety of cellparameters, such as cell resistance, current change and/or derivatives(e.g., first, second) of the voltage-time curve. For example, information process 200, method 400 may further comprise graduallyincreasing a C-rate, equivalent to increasing the charging current,during at least the first cycle, gradually, possibly to follow specifiedthresholds (stage 435), e.g., from at most C/50 to at most C/30. Therate of increasing the charging current may be determined in realtime,with respect to cell measurements as disclosed herein, or may bepredetermined, e.g., according to initial checks, or former experience,modelling or estimations. In certain embodiments, the charging rate atthe first cycle may increase e.g., tenfold (10×), during the firstcycle. In various embodiments, the charging rate at the first cycle mayincrease by between twofold (2×) and one-hundred-fold (×100), during thefirst cycle.

In certain embodiments of formation process 200, method 400 may furthercomprise carrying out at least part of the first cycle at a very lowC-rate—to enhance wettability (stage 440). The inventors have found outthat low initial formation currents (e.g., C/77) enhance electrolytewetting of the electrodes surface due to the potential between thebattery poles. Applying small currents, at least initially, achieveshigh potential difference between the positive and negative terminalsand enhances the wetting process. For example, the initial formationcurrent may be any of C/60, C/70, C/80 or lower charge rates. In certainembodiments, the charging in the first cycle may be performed at a rateof less than C/50 at least during a third of a charging duration. Incertain embodiments, the first cycle may be carried out by graduallyincreasing a charging current, during the first cycle, from at most C/70to at most C/50 during at least a third of a charging duration. Incertain embodiments, low initial formation currents may be appliedduring shorter or longer parts of the first cycles, e.g., during 1/10, ⅕or ¼ of the duration of the first cycle; of alternatively during ½ or ⅔of the duration of the first cycle, respectively. For example, Table 1provides a non-limiting example for gradual current increases duringfirst cycle 120A. In the example, the charging current may be increasedgradually in five steps (as a non-limiting example), each characterizedby a range of charging currents (expressed in relation to the C-rate)and a range of durations for each of the steps, according to someembodiments of the invention. Each of the steps may be broken down intosmaller steps, or combined with consecutive steps, with its specifictime limitations. The change from step to step may be linear and/orstep-like and/or polynomial of the form aX³+bX²+cX+d, or any other form,where X is the time and a-d are coefficients. In certain embodiments,the current may be raised by any function of the time, step-wise orcontinuously, pre-determined or modified during the first formationcycle. Table 2 provides two non-limiting examples for the gradualcurrent increases and optional voltage increases with differentlimitations, according to some embodiments of the invention

TABLE 1 A non-limiting example for gradual current increases during thefirst formation cycle. Lower Upper Lower Upper charging charging timelimit time limit Step # rate limit rate limit (hours) (hours) 1 0.0125C   0.033 C  0.2 5 2 0.033 C  0.05 C  0.2 5 3 0.05 C  0.1 C 0.2 5 4 0.1C 0.5 C 0.2 5 5 0.5 C   1 C 0.2 5

TABLE 2 two non-limiting examples for the gradual current increases andoptional voltage increases with different limitations. 4.2 V limitation(full charge) 4 V limitation (partial charge) Time V limit Time V limit(hour:min:sec) C-rate (V) (hour:min:sec) C-rate (V) 2:00:00 0.0013 C 3.9Low 2:00:00 0.0013 C 3.8 Low 2:00:00 0.0025 C 3.9 charging 2:00:000.0025 C 3.8 charging 2:00:00 0.0038 C 3.9 currents, 2:00:00 0.0038 C3.8 currents. 2:00:00 0.0050 C 3.9 Voltage 2:00:00 0.0050 C 3.8 2:00:000.0063 C 3.9 increases. 2:00:00 0.0063 C 3.8 2:00:00 0.0075 C 3.92:00:00 0.0075 C 3.8 2:00:00 0.0088 C 3.9 2:00:00 0.0088 C 3.8 2:00:000.0100 C 3.9 2:00:00 0.0100 C 3.8 2:00:00 0.0113 C 3.9 2:00:00 0.0113 C3.8 2:00:00 0.0125 C 3.95 2:00:00 0.0125 C 3.8 2:00:00 0.0375 C 4Gradual 2:00:00 0.0250 C 3.8 2:00:00 0.0500 C 4 current 2:00:00 0.0375 C3.8 2:00:00 0.0625 C 4 increase. 2:00:00 0.0500 C 3.8 1:00:00 0.0750 C 4Gradual 2:00:00 0.0625 C 3.8 0:55:00 0.0875 C 4 duration 1:00:00 0.0750C 3.8 Gradual 0:50:00 0.1000 C 4 decrease. 0:55:00 0.0875 C 3.8 current0:45:00 0.1125 C 4 0:50:00 0.1000 C 3.8 increase. 0:40:00 0.1250 C 40:45:00 0.1125 C 3.8 Gradual 0:35:00 0.1375 C 4 0:40:00 0.1250 C 3.8duration 0:30:00 0.1500 C 4 0:35:00 0.1375 C 3.8 decrease. 0:25:000.1625 C 4 0:30:00 0.1500 C 3.8 0:20:00 0.1750 C 4 0:25:00 0.1625 C 3.80:20:00 0.1875 C 4 0:20:00 0.1750 C 3.8 0:20:00 0.2000 C 4 0:20:000.1875 C 3.8 0:20:00 0.2125 C 4 0:20:00 0.2000 C 3.8 0:20:00 0.2250 C 40:20:00 0.2125 C 3.8 0:20:00 0.2375 C 4 0:20:00 0.2250 C 3.8 0:20:000.2500 C 4 0:20:00 0.2375 C 3.8 0:20:00 0.2625 C 4 0:20:00 0.2500 C 3.80:20:00 0.2750 C 4 0:20:00 0.2625 C 3.8 0:20:00 0.2875 C 4 0:20:000.2750 C 3.8 0:20:00 0.3000 C 4 0:20:00 0.2875 C 3.8 0:20:00 0.3125 C 40:20:00 0.3000 C 3.8 0:20:00 0.3250 C 4 0:20:00 0.3125 C 3.8 0:20:000.3375 C 4 0:20:00 0.3250 C 3.8 0:20:00 0.3500 C 4 0:20:00 0.3375 C 3.80:20:00 0.3625 C 4 0:20:00 0.3500 C 3.8 0:30:00 0.3750 C 4 0:20:000.3625 C 3.8 0:20:00 0.3875 C 4 0:30:00 0.3750 C 3.8 0:20:00 0.4000 C 40:20:00 0.3875 C 3.8 0:20:00 0.4125 C 4 0:20:00 0.4000 C 3.8 0:20:000.4250 C 4 0:20:00 0.4125 C 3.8 0:20:00 0.4375 C 4 0:20:00 0.4250 C 3.80:20:00 0.4500 C 4 Voltage 0:20:00 0.4375 C 3.8 0:15:00 0.4625 C 4.05increase to 0:20:00 0.4500 C 3.8 0:10:00 0.4750 C 4.1 limit, 0:15:000.4625 C 3.85 Voltage 0:05:00 0.4875 C 4.15 completion 0:10:00 0.4750 C3.9 increase to 12:00:00  0.5000 C 4.2 of the first 0:05:00 0.4875 C3.95 limit, cycle. completion 4:00:00 0.5000 C 4 of the first cycle.

In certain embodiments of formation process 200, method 400 may furthercomprise applying narrowed voltage ranges in the consecutive formationcycles (stage 450). In certain embodiments of formation process 200,method 400 may further comprise adjusting the discharge current rangesin the consecutive formation cycles (stage 460). For example, in theconsecutive charge-discharge cycles of the formation process, thebattery may be charged and discharged to any value between a specifiedrange of the maximal cell capacity in each of the cycles. Charging anddischarging may be carried out to different values with the specifiedrange in different cycles. The specified range may be, e.g., 30%-80%,20%-80%, 10%-90% or sub-ranges thereof.

FIG. 5 provides a non-limiting example for formation process 200,according to some embodiments of the invention. In the illustratednon-limiting example, the first formation cycle may be carried out atC₀/30 rate to full charge (cycles 120A) with current adjustments (stage430) according to feedback 106 relating to any of the disclosedcharacteristics of the cell and its charging parameters, followed bypartial discharge, and consecutive cycles may comprise a second cycle atC₁/10 (Cycle 120B—first) and two cycles (120B) at C₂/5, with C₁ denotingthe discharge capacity measured or estimated after the first cycle andC₂ denoting the discharge capacity measured or estimated after thesecond cycle. In this example, overall formation time was shortened to80 hours, while maintaining the lifetime improvement.

The inventors suggest, without being bound by theory, that limitingand/or adjusting the charging currents and/or voltage ranges may preventparasitic processes at the electrode-electrolyte interfaces which do notcontribute to the proper formation of the SEI and may even deterioratethe quality of the SEI (see e.g., Ning and Popov 2004, Cycle LifeModeling of Lithium-Ion Batteries, Journal of the ElectrochemicalSociety, 2004, pages A1584-A1591), later to be manifested in shortercycling lifetime.

Feedback 106 which may serve to adjust the charging currents or anyother of the formation process parameters (see FIG. 1) such as voltageranges and used currents in charging and/or discharging, as well ascurrent/voltage step durations and other parameters—according to variouspredetermined criteria and/or measured parameters during the formationprocess such as time, resistance, capacity, voltages (when currents arepre-determined), currents (when voltages are pre-determined) etc., aswell as temporal derivatives of the battery parameters and the formationprocess parameters.

FIG. 6 provides a non-limiting example that illustrates, according tosome embodiments of the invention, the additional improvement in cyclelifetime when using current adjustments in the first cycle as disclosedabove (stage 430, FIG. 5) with respect to using a constant chargingcurrent in the first cycle (FIG. 4)—in the non-limiting example cyclelife time is improved by ca. 15%. FIG. 6 illustrates the normalizedcapacity of the cells over their cycling life, under operationconditions of 10 C charging and C/2 discharging, with a dynamic voltagevariation cycling procedure described below—the operation voltage rangestarting at narrow range 140, of 3-4.2V, and is broadened, stepwise 140A. . . N, as the capacity deteriorates, until reaching the widest voltageoperation range 145 (see, e.g., FIG. 13).

FIG. 7 is a non-limiting example of two formation processes 200,according to some embodiments of the invention. Both processes employcurrent adjustments 430—(i) in one first cycle 120A with voltage rangebetween 3-4V; and (ii) in two first cycles 120A (first) and 120A(second) with voltage range between 3-4.2V. The inventors have found outthat process (i) takes 39 hours for the formation process with respectto 51 hours for process (ii), and while process (i) results in a lowercapacity of the formed cell by ca. 3-3.5% (depending on the chargingrate) with respect to process (ii), it provides a cycle life time whichis longer by ca. 10%—383 hours for process (i) versus 349 hours forprocess (ii). This non-limiting example illustrates the ability totrade-off cycle lifetime with resulting capacity, which enables thedisclosed optimization of the formation process. It is noted thatpartial discharge in the formation cycles, as disclosed herein (notreaching 100% DoD) further increased the cycle life of the formedbatteries. It is emphasized that both variations provide higher cellcapacity and longer cycle life, as well as shorter formation duration,with respect to prior art formation processes, and with respect toformation processes such as demonstrated in FIG. 4.

FIG. 8 is a high-level schematic illustration of a fast-charging lithiumion cell 90 being charged in a SEI formation process 401, characterizedby cell cycling configurations 120, according to some embodiments of theinvention. The inventors have found out that reducing the formationvoltage (at a constant voltage phase of charging)—during the firstformation charging cycle and/or during consecutive formation chargingcycles, may yield efficient formation and increased anode capacity.

FIG. 8 illustrates schematically cell 90 comprising cathode 94, cellseparator 98, electrolyte 96 and anode 92 (and/or anode materialparticles 150, see FIG. 19 below) on which SEI 95 is formed at theinterface between anode 92 and electrolyte 95. The SEI formation processis carried out over the first cycles of charging and discharging cell 90by electrochemical interactions of lithium ions Li⁺ moving fromelectrolyte 96 to anode 92, and being reduced on the anode surface,forming the SEI. While most Li⁺ are intercalated in anode 92 (denoted asLi⁻⁰¹, for intercalated lithium atoms), some Li⁺ are reduced on theanode surface (denoted as Li⁰), forming the SEI which functions as abarrier during the later operation of cell 90, which prevents orsignificantly reduce further Li⁺ reduction and support effectivelithiation and release of Li⁺ with minimal loss of cell capacity. Cell90 is charged and discharged in the first cycles by a charging system100 configured to charge and discharge cell 90 during the formationprocess, which has controller, or a charging management module 105,which determines the charging and discharging ranges in one or morefirst cycle(s) 110 and consecutive one or more cycles 115. It is notedthat the formation processes are carried out at the factory, prior todelivery of the batteries to the end users. While prior art SEIformation process is carried out by fully charging and fully dischargingthe cell once or more, the inventors suggest, without being bound bytheory, that partial charging and/or discharging in at least some of theSEI formation cycles provides better SEI and longer cell operationlifetime. It is noted that the disclosed formation process may becarried out on graphite-based anodes 92 and/or on anodes 92 made of anyof other materials, such as metalloids—Si, Ge and/or Sn, as disclosedbelow (see FIG. 19).

In some embodiments, SEI formation 120 may be carried out by performingfirst cycle 110 of fully charging cell 90 and consecutively fully orpartly discharging cell 90 (e.g., discharging cell 90 from 100%, 90%,85% or intermediate values, of cell capacity, or DOD—depth ofdischarge), and consecutively, performing a plurality ofcharge-discharge cycles 115, in which cell 90 is charged and dischargedto between 10-100% of maximal cell capacity in each of cycles 115(formation scheme 120A). For example, first cycle 110 may be carried outat e.g., 0.1 C, 0.03 C, 0.01 C or values in-between, and consecutivecycles 115 may be carried out at 0.2 C, 0.1 C, 0.05 C, possibly highervalues such as 0.5 C or even 1 C, or values in-between. In certainembodiments, first cycle 110 may be carried out at a variable rate,starting e.g., from 0.1 C, 0.03 C, 0.02 C, 0.01 C or values in-betweenand increasing (e.g., step-wise and/or gradually) during the first cycleto e.g., 0.2 C, 0.3 C, 0.5 C, possibly to higher values such as 1 C orvalues in-between, until the end of the first cycle.

In some embodiments, SEI formation 120 may be carried out by performingfirst cycle 110 of charging cell 90 to any value between a specifiedrange of a full cell capacity (e.g., 30%-80%, 20%-80%, 10%-90% orsub-ranges thereof) and consecutively fully or partly discharging cell90 (e.g., discharging cell 90 from 100%, 90%, 85% or intermediatevalues, of cell capacity, or DoD), and consecutively, performing aplurality of charge-discharge cycles 115, in which cell 90 is charged100% of maximal cell capacity and then fully or partly discharged (e.g.,discharging cell 90 from 100%, 90%, 85% or intermediate values, of cellcapacity, or DoD), in each of cycles 115 (formation scheme 120B). Forexample, first cycle 110 may be carried out at e.g., 0.1 C, 0.03 C, 0.01C or values in-between, and consecutive cycles 115 may be carried out at0.2 C, 0.1 C, 0.05, or values in-between.

FIG. 8 further illustrates fast-charging lithium ion cell 90 beingcharged in SEI formation process 120, according to some embodiments ofthe invention, with illustrated embodiments 120C, 120D, 120E, 120F offormation process 120 all use a lower current level than the fullcurrent used in prior are formation processes. The inventors have foundout that optimizing the formation current (at a phase prior to constantvoltage of charging), may yield efficient formation and increased anodecapacity.

In certain embodiments, multiple formation cycles may be applied,starting at a low level of current and gradually, from cycle to cycle,increasing the charging current, possibly until reaching the fullcurrent in later formation cycles. The following non-limiting examplesare shown: formation scheme 120C having more than three cycles (denotedfirst 110, second 115A, third 115B and consecutive 115 cycles);formation scheme 120D having three cycles (first 110, second 115A andthird 115B cycles); formation scheme 120E having two cycles (first 110and second 115A cycles); and formation scheme 120F having a single cycle(first cycle 110) using a low current (possibly gradually raisedcurrent, see, e.g., FIG. 5).

In certain embodiments, formation process 120 may be carried out in asingle charging cycle 110 using a reduced level of current. In certainembodiments, charging current level during first cycle 110 may bechanged during the formation process (illustrated schematically by thedashed line in scheme 120F), possibly according to measurement ofvarious parameters of cell 90 during formation 120, such as cellresistance, current change and/or derivatives of the voltage-time curve(see e.g., FIG. 5), such as the first and/or second derivative.

In certain embodiments, charging cell 90 in first cycle(s) 110 and/orconsecutive cycle(s) 115 is carried out with respect to an estimatedamount of charge delivered to and from anode 92 respectively. Theinventors have found out that managing the amount of charge moved to andfrom the anode enables better control of the SEI formation process. Incertain embodiments, resulting fast-charging lithium ion cells 90 haveimproved lifetime due to improved SEI stability and function andpossibly improved anode and cell capacity.

Returning to FIG. 3, formation method 200 may comprise the followingstages, irrespective of their order. The method stages may be carriedout with respect to cells 90 described herein, which may be configuredto implement methods 200. Method 200 may be at least partiallyimplemented by at least one computer processor, implemented e.g. incharging management module 105, which controls the charging anddischarging of cell 90. Certain embodiments comprise computer programproducts comprising a computer readable storage medium having computerreadable program embodied therewith and configured to carry out relevantstages of method 200. Method 200 may comprise stages for producing,preparing and/or using cell 90, such as any of the following stages.

Method 200 comprises preparing a fast-charging lithium ion cell for useby forming a SEI in the anode (stage 210), for example by performing afirst cycle of fully charging the cell and consecutively discharging thecell (stage 220), and performing, consecutively, a plurality ofcharge-discharge cycles, in which the cell is charged and discharged tobetween 10-100% of maximal cell capacity in each of the cycles (stage225).

Alternatively, method 200 may comprise performing a first cycle ofcharging the cell to between e.g., 30-70% (possibly 30%-80%, 20%-80%,10%-90% or other ranges) of a full cell capacity and consecutivelydischarging the cell (stage 230), and performing, consecutively, aplurality of charge-discharge cycles, in which the cell is charged toany of e.g., 70%, 80%, 90% or 100% of the full cell capacity and thendischarged, in each cycle (stage 235), in various embodiments, dependingon formation plan and requirements.

For example, the first cycle (stages 220 and/or 230) may be carried outat e.g., 0.03 C and the consecutive cycles (stages 225 and/or 235) maybe carried out at e.g., 0.1 C. In various embodiments, the first cyclemay be carried out at e.g., 0.1 C, 0.03 C, 0.01 C or values in-between,and the consecutive cycles may be carried out at 0.2 C, 0.1 C, 0.05 C,possibly higher values such as 0.5 C or even 1 C, or values in-between.In certain embodiments, the first cycle may be carried out at a variablerate, starting e.g., from 0.1 C, 0.03 C, 0.02 C, 0.01 C or valuesin-between and increasing (e.g., step-wise and/or gradually) during thefirst cycle to e.g., 0.2 C, 0.3 C, 0.5 C, possibly to higher values suchas 1 C or values in-between, until the end of the first cycle.

In certain embodiments, method 200 may comprise preparing afast-charging lithium ion cell for use by forming a solid-electrolyteinterphase (SEI) in the anode, by performing at least a first cycle offully charging the cell and consecutively discharging the cell, whereina first applied charging current in the first cycle is very low e.g.,below C/50, C/60, C/70 etc. (stage 250). Certain embodiments comprisegradually increasing the charging current from cycle to cycle (stage255) and possibly carrying out the formation process in a single lowcurrent charging cycle (stage 260).

Returning to FIG. 2, methods 400 may comprise operating the battery 300initially at a narrow range of voltages (stage 470), e.g., which issmaller than 1.5V and consecutively, upon detection of a specifieddeterioration in a capacity of the battery, operating the battery atleast at one broader range of voltages, e.g., which is larger than 1.5V(stage 480). For example, the narrow range may be within 3-4V and atleast one of the broader range(s) may be within 1.8-4.95V. In anotherexample, the narrow range may be within 3.1-4.3V and at least one of thebroader range(s) may be within 1.8-4.3V. The at least one broader rangemay comprise a plurality of consecutive steps of increasing voltageranges (denoted 140A . . . N), between the narrow range (denoted 140)and a full operation range of the battery (denoted 145). For example,narrow range 140 may be within 3.1-4.3V, the consecutive ranges 140A . .. 140C may be within 3.0-4.3V, 2.8-4.3V, and 2.5-4.3V; and the fullrange 145 may be within 1.8-4.3V.

In certain embodiments, operating the battery 300 may be carried out atrates calculated with respect to the discharge capacity measured orestimated after the last of the consecutive formation cycles (denotedC₂), see Equations 1 above, e.g., at 10 C₂ (charging) and C₂/2(discharging), possibly after adjustments (stage 427) carried out duringformation process 200. Moreover, during the operation of the battery300, method 400 may further comprise adjusting charging currentsaccording to estimations of a deteriorating capacity of the battery(stage 490). In certain embodiments, during the operation of the battery300, method 400 may further comprise ramping up gradually the chargingcurrents during a first third of a charging duration of the battery(stage 492) and possibly adjusting the charging current rampingaccording to estimations of the deteriorating capacity of the battery(stage 495), see FIG. 17 below for an example for current ramping.

FIGS. 9-11 are high-level schematic illustrations of systems 132operating a fast-charging lithium ion battery 90 in gradually increasingvoltage ranges, according to some embodiments of the invention. Systems132 may be at least part of systems 401 configured to increase thecycling lifetime of fast charging lithium ion batteries 90. Batteryunits 130 comprise battery 90 (e.g., as one or more packs or cells) andtypically comprise and/or are associated with a charging managementmodule 135 configured to determine various battery operation parameters(FIG. 9), including the voltages range of operation in supplying powerto devices 82 connected to battery unit 130. Battery unit 130 mayfurther comprise and/or be associated with a SOH (state of health)and/or SOC (state of charge) monitor 137 which monitors batteryperformance parameters such as resistance and capacitance thereof. Invarious configurations of systems 132, at least one fast-charginglithium ion battery 90 may be operatively associated with one (or more)battery management unit(s) 135 configured to modify a range of voltagelevels supplied by or to battery unit(s) 130 according to a state ofhealth of the battery, any of battery parameters (e.g., resistance,estimated capacity, state of charge, etc.) starting from an initialnarrow range and reaching a full voltage range (e.g., narrow rangespanning less than 1.5V and the full range spanning more than 2V), asexemplified below. In certain embodiments, the initial narrow range maybe any of 30%, 50%, 70% or any intermediate value of the full operativerange of the battery.

In some embodiments, charging management module 135 and/or SOH/SOCmonitor 137 may be part of an operating module 131 (illustratedschematically in FIG. 10) which may be a unit external to battery unit130 and in communication thereto and/or contact therewith. Either orboth charging management module 135 and SOH/SOC monitor 137 may bepacked separately from fast-charging lithium ion battery 90, e.g. asoperating module 131.

In some embodiments, charging management module 135 (or 135A) and/orSOH/SOC monitor 137 may be part of an operating module 131 (illustratedschematically in FIGS. 10 and 11) which may be in bi-directionalcommunication with charger 80 and/or with device 82. In certainembodiments (see e.g., FIG. 11), at least part of the chargingmanagement may be carried out by a charging management module 135B incharger 80 which may be configured to complement or replace a chargingmanagement module 135A in operation module 131 (or in battery unit 130as illustrated schematically in FIG. 9). Communication between chargingmanagement module 135B in charger 80 and charging management module 135Ain operation module 131 and/or charging management module 135 in batteryunit 130 may be bi-directional.

Charging management module 135 may be in communication with a powermanagement module 84 in device 82 to coordinate parameters of thesupplied power and ensure proper operation of device 82 at the setvoltages ranges.

Battery units 130 may be configured, typically by configuring chargingmanagement module 135, to modify a range of voltage levels supported bybattery unit 130 according to a state of battery 90, starting from aninitial narrow range of operation 140 and reaching a consecutive widerrange of operation 145 as the battery's cell resistance increases. Thevoltages range modification may be carried out with respect to anestimated resistance of battery 90 and to maximize a capacity of battery90, e.g., according to data from SOH/SOC monitor 137. For example,modifying the voltage range may be implemented by increasing a chargingvoltage upper limit and/or by decreasing a discharging voltage lowerlimit. In some embodiments, narrow range 140 may be between 3-4V and thewider range 145 may be between 1.8-4.95V.

In certain embodiments, battery management unit 135 may be configured tomodify the voltage range in a plurality of consecutive steps ofincreasing voltage ranges, between initial narrow range 140 and fullrange 145.

In certain embodiments, a width of narrow range 140 may be around 1V,e.g., 2.8-3.8V, 3-4V, 3.2-4.2V, possibly also smaller such as 0.8V,e.g., 2.8-3.6V, 3-3.8V, 3.2-4V, possibly also larger such as 1.2V, e.g.,2.8-4V, 3-4.2V.

In certain embodiments, a width of narrow range 140 may be around 3V,e.g., 1.8-4.8V, 2-5V, possibly also smaller such as 2.5V, e.g.,1.8-4.3V, 2-4.5V, 2.2-4.7V, possibly also larger such as 3.2V, e.g.,1.6-4.8V, 1.8-5V.

Advantageously, without being bound by theory, as fast chargingbatteries 90 have low resistance, they enable the widening of thevoltage range (from narrow range 140 to wider range 145) to increasetheir capacity with respect to the prior art.

Charging battery 130 by a corresponding charger 80 may be carried out incorresponding narrow and wider ranges in different operation stages ofbattery, which may be similar to narrow and wider ranges 140, 145 thatare used during discharging battery 90 to operate device 82.

Certain embodiments comprise fast-charging lithium ion battery units 130comprising one or more corresponding battery management units 135configured to modify a range of voltage levels supplied by battery 90according to a state of health of the battery, starting from a narrowrange and reaching a wider range.

Returning to FIG. 3, operation method 300 may comprise the followingstages, irrespective of their order. The method stages may be carriedout with respect to batteries 90 and/or battery units 130 describedherein, which may be configured to implement methods 300. Method 300 maybe at least partially implemented by at least one computer processor,implemented e.g. in charging management module 135, which controls theenergy supply by battery unit 130 to device 82. Certain embodimentscomprise computer program products comprising a computer readablestorage medium having computer readable program embodied therewith andconfigured to carry out relevant stages of method 300. Method 300 maycomprise stages for producing, preparing and/or using batteries 90and/or battery unit(s) 130, such as any of the following stages,irrespective of their order.

Method 300 comprises operating a device, using a fast-charging lithiumion battery, by managing operation voltages of the battery to increaseits lifetime (stage 305), for example by modifying a range of voltagelevels supplied by the battery according to a state of the battery(stage 310), starting from a narrow range and reaching a wider (possiblya full) range (stage 330).

In certain embodiments, method 300 may further comprise modifying arange of voltage levels at which the battery is charged according to astate of the battery (stage 315), with respect to any of a plurality ofbattery parameters such as resistance, state of charge, capacity etc.Modifying 310 (and optionally 315) the range(s) may be carried out withrespect to, and to minimize the remaining capacity of the battery (stage317) and/or to minimize a capacity fade of the battery. The voltagerange may be modified out in a plurality of consecutive steps ofincreasing voltage ranges (stage 318), between the initial narrow rangeand the full range, starting e.g., from an initial narrow range which isany of 30%, 50%, 70% or any intermediate value of the full operativerange of the battery (stage 319).

Method 300 may further comprise monitoring the state of charge and/orstate of health of the battery to determine the operation ranges (stage320), and carry out modifications 310 (and optionally 315) accordingly.

Modifying 310 (and optionally 315) may be carried out with respect to anestimated resistance of the battery and to maximize a capacity of thebattery.

Modifying 310 (and optionally 315) may be implemented by increasing acharging voltage upper limit (stage 332) and/or by decreasing adischarging voltage lower limit (stage 334).

In some embodiments, the narrow range is 3-4V and the wider range may be1.8-4.95V. In some embodiments, the narrow range is any of 3.1-4.3V,3.0-4.3V, 2.8-4.3V, and 2.5-4.3V; and the full range may be 1.8-4.3V.

In certain embodiments, method 300 further comprises reducing thecharging current as the cell capacity decreases (stage 340) and/orincreasing the duration of the constant current charging phase as thecell performance deteriorates (stage 350).

In certain embodiments, method 300 further comprises introducing,intermittently, sets of few (e.g., 1-10) full voltage range cyclesconfigured to redistribute lithium ions in anode material particles ofthe battery (stage 360), as explained below (see FIG. 20C).

FIG. 12 is a high-level schematic illustration of controlling theparameters for operating a fast-charging lithium ion battery unit 130 orbattery 90 in multiple voltage ranges 140, according to some embodimentsof the invention. As the cell resistance increases and the cellcapacitance decreases, any of the following operation parameters may bechanged accordingly: The operation voltage range may be modified asdisclosed herein, e.g., extended from voltage range(s) which extend overless than 1.5V to voltage range(s) which extend over more than 1.5V;from high charging current to lower charging currents, either at C-rateswhich correspond to the deteriorating battery capacity or according topredefined parameters; and/or from shorter durations of the constantcurrent stage with respect to the constant voltage stage (CC/CV) tolonger durations of the constant current stage with respect to theconstant voltage stage (see e.g., FIG. 16B). In certain embodiments, theoperation voltage range may be modified with respect to the battery's DC(direct current) resistance value which may be monitored occasionally(e.g., after any predefined number of cycles), and used to definethreshold(s) for triggering the change of voltage range and/or thechange of charging current (and see below).

The control of the illustrated operation parameters may be carried outby charging management module 135, 135A, possibly as specified operationschemes, and possibly incorporating monitoring and/or feedback 137A bySOH/SOC monitor 137. Any of the elements of the illustrated schemes maybe applied independently or in combination with other elements, and byany of the embodiments of charging management module 135, 135A. Based ondata from SOH/SOC monitor 137 and/or independently therefrom, chargingmanagement module 135, 135A may be configured to control any of thefollowing parameters as cell resistance increases, cell capacitancedecreases and/or time passes: The voltage range may be graduallyincreased and/or the charging current (in the constant current, CC,phase of charging) may be decreased (e.g., as cell capacitancedecreases). Any of these changes may be carried out gradually and/orstepwise. It is noted that while these parameters are related and partlydependent on each other, operation optimization may be configured tocontrol one or more of these parameters, indirectly determining theother parameters as well. See, e.g., FIGS. 16A-C for non-limitingexamples.

FIG. 13 is a high-level schematic illustration of operating afast-charging lithium ion battery unit 130 or battery 90 in multiplevoltage ranges 140, according to some embodiments of the invention. Anyof disclosed charging management modules 135 may be configured tooperate battery unit 130 or battery 90 in a variety of voltage ranges(cumulatively included in an operation pattern 143), having continuouslyor step-wise changing lower limits and possibly upper limits. Forexample, FIG. 13 exemplifies stepwise increases in the extent of theoperation voltage range, which are related to the increasing cellresistance. In the illustrated non-limiting examples, voltage ranges of3.1-4.3V as initial narrow range of operation 140, 3.0-4.3V as a widerrange of operation 140A, 2.8-4.3V as a still wider range of operation140B, 2.5-4.3V as a still wider range of operation 140C, and 1.8-4.3V asfull range of operation 145, as the cell resistance exceeds a specifiedthreshold. FIG. 13 further illustrates schematically the operation ofbattery unit 130 with N intermediate and sequentially increasing voltageranges (140A, 140B, . . . , 140N) between initial narrow range and fullrange 145. Changes from each voltage range to the next may be appliedwith respect to various parameters, such as time, SOH, SOC, cellcapacity, cell resistance, etc.

FIGS. 14A and 14B demonstrate results that indicate the improvedperformance of fast charging battery unit(s) 130 when operated accordingto the disclosed scheme, according to some embodiments of the invention.FIG. 14A illustrates the cycle life (number of cycles) and energy (mWh)of cells operated at 10 C charging rate at four different initialvoltage ranges 140, namely of 3.1-4.3V, 3.0-4.3V, 2.8-4.3V and 2.5-4.3Vthroughout the operation of the cell. In all four cases, the operationvoltage range was gradually increased from respective initial voltageranges 140 until full range 145 1.8-4.3V was reached. As illustrated inFIG. 14A, operation of the cell at initial narrow voltages ranges 140smaller than 1.5V increases the cycle life twofold to threefold withrespect to cell operation with full voltage range 145 from the beginningof the cycling (e.g., for an initial voltage operation range of 1.2Vcycle life was more than doubled with respect to an initial voltageoperation range of 1.8V). Moreover, the narrower the initial operationrange is, the higher is the achieved cell energy. It is noted also, thatthe narrower the initial operation range is, the larger is theflexibility in consequent operation of the cell with respect to thevoltage range. FIG. 14B illustrates the cycle life of two of the fouroperation schemes in more detail, illustrating the long life cycleachieved by initial narrow voltages 140 ranges smaller than 1.5V (shownfor 3.1V-4.3V cycles, with the maximal and minimal cut off voltagelevels illustrated in solid lines)—providing long cycle life of thecells, ca. 300 cycles in the illustrated, non-limiting example, withrespect to prior art initially broad voltage range (shown for 2.5V-4.3V,with the maximal and minimal cut off voltage levels illustrated inbroken lines)—providing short cycle life of the cells, ca. 100 cycles.

FIG. 15 provides a non-limiting example for the increased cycle lifetimeof battery 90 operated with adjusted charging currents according to thedeteriorating capacity of battery 90 (stage 490), according to someembodiments of the invention. FIG. 15 illustrates a comparison of cellcapacity retention of 1 Ah cells over their cycling life, underoperation conditions of 10 C charging and C/2 discharging with currentadjustments that correspond to the declining cell capacity (see, e.g.,FIG. 16A below) in addition to the dynamic voltage variation cyclingprocedure described above—the operation voltage range starting at narrowrange 140, of 3-4.2V, and is broadened, stepwise 140A . . . N, as thecapacity deteriorates, until reaching the widest voltage operation range145.

FIGS. 16A-C provide examples for current adjustments corresponding tocell deterioration 490, according to some embodiments of the invention.FIG. 16A-16C refer to the same operation pattern of the battery,illustrated with respect to the maximal and minimal charging currents(FIG. 16A), ratio of constant current (CC) stage to total cycle duration(FIG. 16B) and cell DC resistance during charging and discharging (FIG.16C).

FIG. 16A provides a non-limiting example for the maximal and minimalcycling currents and their adjustment with capacity degradation duringincreasing cycle numbers, according to some embodiments of theinvention. In the illustrated example, the maximal current is reducedstepwise after the 200^(th) cycle (indicated by the arrow), at threesteps of decrease: 11 A, 10.3 A, 9.9 A. The current adjustments may bedetermined in dependency on the cell degradation, e.g., using a newcurrent value which equals the cell capacity decrease (the ratio ofcapacity at specific cycle to the initial cell capacity value) times theinitial maximal current (used to charge the cell at the beginning of thecycle life) optionally times a multiplication factor (e.g., between 0.85and 1.2). For example, if the initial charging current is 10 A and thecell capacity decrease is 85%, then the adjusted charging current may bedecreased to 8.5 A (assuming 1 as multiplication factor).

FIG. 16B provides a non-limiting example for the duration of the CCstage from the total cycle duration during increasing cycle numbers,according to some embodiments of the invention. The decreased durationof the CC stage during cycles 100 to 200 may be increased by the currentadjustments starting in cycle 200, indicating that decreasing thecharging current actually helps in maintaining the charge more in the CCmode. In certain embodiments, the charging current may be changed tovalues that equal the initial maximal current times the ratio between CCand total charging times, optionally times a multiplication factor(e.g., between 0.85 and 1.2). For example, if the initial chargingcurrent is 10 A and the percentage of CC stage from total cycle is 80%,then the adjusted charging current may be decreased to 8 A (assuming 1as multiplication factor) to approach full cycling at constant current(CC).

FIG. 16C provides a non-limiting example for the increase in cell DCresistance to charging and to discharging, during increasing cyclenumbers, according to some embodiments of the invention. Thresholdvalue(s) may be set along the increasing resistance curves, fortriggering any of current decrease, voltage range increase and theirmagnitudes. For example, the adjusted current value may be set to equalthe initial maximal current times the ratio between and initial andlater DC resistance values, optionally times a multiplication factor(e.g., between 0.85 and 1.2). For example, if the initial chargingcurrent is 10 A and the DC resistance values ratio is 0.72, then theadjusted charging current may be decreased to 7.2 A (assuming 1 asmultiplication factor).

Certain embodiments may combine the considerations presented above andcontrol the charging current adjustments according to any combination ofthe cell capacity, the duration of the CC stage, the DC resistance andpossibly of related characteristics.

FIG. 17 provides a non-limiting example for current ramping (see e.g.,stage 492, 495) at the beginning of charging during battery operation,according to some embodiments of the invention. The inventors have foundout that current ramping may decrease the probability of dendriteformation and lithium concentration differences, which may lead tobattery failure. Particularly when using high currents applied in fastand ultra-fast charging, there is a need to overcome potential threatsas lithium dendrite formation on the anode side, which could cause inturn further dendrite growth, separator penetration, and eventuallyshort circuit of the cell. In addition, while applying high currentdensities, on the electrode/electrolyte interface, there could be verylarge differences in lithium ion concentrations at theelectrode/electrolyte interface, resulting in areas with lithium iondeficiency and areas with elevated lithium ion concentration—which maycause local rise in resistance and local heating, enhancing electrolytedecomposition on both the anode and the cathode.

Charging currents may be initially ramped up, gradually increased, toprevent dendrite formation and lithium concentration differences.Various forms of current ramping may be applied and optimized, such aslinear ramping (I=aT+b), quadratic ramping (I=aT²+bT+c), or any otherpolynomial ramping (e.g., I=aT³+bT²+cT+d), or other increasingfunctional forms (e.g., I=a·sin(bT)), in all of which I denoting thecurrent value, T the time and a to d are coefficients. Clearly, rampingmay be carried out stepwise from zero to a specified value, possiblywith intermissions between steps, as presented in a non-limiting examplein Table 3, with t1-t13 indicating consecutive time points between zeroand full charging.

TABLE 3 a non-limiting example for a current ramping procedure duringbattery operation. Time unit C-rate range t1 0.1 C-0.99 C   t2 1 C-1.99C t3 2 C-2.99 C t4 3 C-3.99 C t5 4 C-4.99 C t6 5 C-5.99 C t7 6 C-6.99 Ct8 7 C-7.99 C t9   8-8.99 C  t10   9-9.99 C  t11 10 C-11.99 C  t12 12C-14.99 C  t13 15 C-20 C  

For example, FIG. 17 illustrates, in three consecutive graphs, a fullview of voltage and current vs. time during operation, a singlecharge-discharge cycle therefrom, and current ramping in the cycle. Inthe non-limiting example, current ramping was performed in a step-wisemode with additions of 1 C current each second, up to current of 8 C atthe end.

FIG. 18A illustrates the cell temperature during cycling (operation ofbattery 90) with current adjustments corresponding to cell deterioration490, according to some embodiments of the invention, compared to FIG.18B illustrating the cell temperature during cycling (operation ofbattery 90) with constant values for the charging currents (with dynamicvoltage range). Illustrated are the minimal temperatures (at the end ofdischarging in each cycle, bottom two lines in each graph) in two runsin each of the operation patterns, and the maximal temperatures (at theend of charging in each cycle, top two lines in each graph) in the tworuns in each of the operation patterns. It is noted that currentadjustments reduce the temperature of the operating battery be severaldegrees (e.g., reduce the average temperature from ca. 38° C. to ca. 35°C. and reduce the maximal temperature from ca. 39° C. to ca. 36° C., oreven lower), a factor which may contribute further to extending thecycling lifetime of battery 90.

FIG. 19 is a high-level schematic illustration of various anodeconfigurations, according to some embodiments of the invention. FIG. 19illustrates schematically, in a non-limiting manner, a surface of anode92, which may comprise anode active material particles 150. Anode activematerial particles 150 may be of various types, at least some of whichcomprising particles of metalloids such as silicon, germanium and/ortin, and/or possibly particles of aluminum, lead and/or zinc, and/orSn-decorated graphene active material particles, as well as forms oflithium titanate (LTO), their alloys and/or mixtures, and possiblyparticles of graphite and/or graphene. Anode active material particles150 may be at diameters in the order of magnitude of 100 nm (e.g.,100-500 nm), and/or possibly in the order of magnitude of 10 nm or 1μ.At least some of anode active material particles 150 may possiblycomprise composite particles 155, e.g., core-shell particles in variousconfigurations. Anode active material particles 150 may compriseparticles at different sizes (e.g., in the order of magnitude of 100 nm,and/or possibly in the order of magnitude of 10 nm or 1μ)—for receivinglithiated lithium during charging and releasing lithium ions duringdischarging. At least some of composite particles 155 may be based onSn-decorated graphene active material particles 150 as their cores.

Anodes 92 may further comprise binder(s) and additive(s) 102 as well asoptionally coatings 170 (e.g., conductive material such as carbon fibersand/or nanotubes 169, conductive polymers, lithium polymers, etc.).Coatings 170 may be applied to patches or parts of the surface of anode92, and/or coatings 160 which may be applied onto anode materialparticles 150, and/or coatings 164 which may be configured as shellswith anode material particles 150 as cores, and/or conductive material169 such as carbon fibers and/or nanotubes may be configured tointerconnect anode material particles 150 and/or interconnect anodematerial particles 150 as cores of core-shell particles 155. Activematerial particles 150 may be pre-coated by one or more coatings 160(e.g., by carbon coating 160, conductive polymers, lithium polymers,etc.), have borate and/or phosphate salt(s) 128 bond to their surface(possibly forming e.g., B₂O₃, P₂O₅ etc.), bonding molecules 180(illustrated schematically) which may interact with electrolyte 96(and/or ionic liquid additives thereto) and/or various nanoparticles 112(e.g., B₄C, WC, VC, TiN, possibly Si and/or Sn nanoparticles), formingmodified anode active material particles 150A, which may be attachedthereto in anode preparation processes 149 such as ball milling (see,e.g., U.S. Pat. No. 9,406,927, which is incorporated herein by referencein its entirety), slurry formation, spreading of the slurry and dryingthe spread slurry. Nanoparticles 112 may have diameters smaller than thediameters of anode active material particles 150, e.g., in the order ofmagnitude of 10 nm (e.g., 10-50 nm). For example, anode preparationprocesses 149 may comprise mixing additive(s) 102 such as e.g.,binder(s) (e.g., polyvinylidene fluoride, PVDF, styrene butadienerubber, SBR, or any other binder), plasticizer(s) and/or conductivefiller(s) with a solvent such as water or organic solvent(s) (in whichthe anode materials have limited solubility) to make an anode slurrywhich is then dried, consolidated and is positioned in contact with acurrent collector (e.g., a metal, such as aluminum or copper).

In certain embodiments, bonding molecules 180 comprise any of themolecules disclosed in WIPO Document No. PCT/IL2017/051358, which isincorporated herein by reference in its entirety; non-limiting examplescomprise lithium alkylsulfonate, poly(lithium alkylsulfonate), lithiumsulfate, lithium phosphate, lithium phosphate monobasic,alkylhydroxamate salts and their acidic forms; for example—lithium4-methylbenzenesulfonate, lithium 3,5-dicarboxybenzenesulfonate, lithiumsulfate, lithium phosphate, lithium phosphate monobasic, lithiumtrifluoromethanesulfonate, lithium 4-dodecylbenzenesulfonate, lithiumpropane-1-sulfonate, lithium1,1,2,2,3,3,4,4,5,5,6,6,7,7,8,8,8-heptadecafluorooctane-1-sulfonate,lithium 2,6-dimethylbenzene-1,4-disulfonate, lithium2,6-di-tert-butylbenzene-1,4-disulfonate,3,3′-((1,2-dithiane-4,5-diyl)bis(oxy))bis(N-hydroxypropanamide),3,3′-((4-mercapto-1,2-phenylene)bis(oxy))bis(N-hydroxypropanamide),lithium aniline sulfonate (the sulfonate may be in any of para, meta andortho positions) as well as poly(lithium-4-styrenesulfonate) applied incoating the anode material particles.

Certain embodiments comprise anode material particles 150 comprising anyof silicon active material, germanium active material and/or tin activematerial, possibly further comprising carbon material, boron and/ortungsten. As non-limiting examples, anode material particles 150 maycomprise 5-50 weight % Si, 2-25 weight % B and/or 5-25 weight % W, and0.01-15 weight % C (e.g., as carbon nanotubes, CNT); anode materialparticles 150 may comprise 5-80 weight % Ge, 2-20 weight % B and/or 5-20weight % W, and 0.05-5 weight % C (e.g., as carbon nanotubes, CNT);anode material particles 150 may comprise 5-80 weight % Sn, 2-20 weight% B and/or 5-20 weight % W, and 0.5-5 weight % C (e.g., as carbonnanotubes, CNT); anode material particles 150 may comprise mixtures ofSi, Ge and Sn, e.g., at weight ratios of any of at least 4:1 (Ge:Si), atleast 4:1 (Sn:Si) or at least 4:1 (Sn+Ge):Si; anode material particles150 may comprise aluminum and/or any of zinc, cadmium and/or lead,possibly with additions of borate and/or phosphate salt(s) as disclosedbelow.

Certain embodiments comprise anode material particles 150 comprisingnanoparticles 112 attached thereto, such as any of B₄C, WC, VC and TiN,possibly having a particle size range of 10-50 nm and providing 5-25weight % of modified anode material particles 150A. Nanoparticles 112may be configured to form in modified anode material particles 150Acompounds such as Li₂B₄O₇ (lithium tetra-borate salt, e.g., via4Li+7MeO+2B₄C→2Li₂B₄O₇+C+7Me, not balanced with respect to C and O, withMe denoting active material such as Si, Ge, Sn etc.) or equivalentcompounds from e.g., WC, VC, TiN, which have higher affinity to oxygenthan the anode active material.

Certain embodiments comprise anode material particles 150 comprisingcoatings(s) 160 of any of lithium polymers, conductive polymers and/orhydrophobic polymers, such as e.g., any of lithium polyphosphate(Li_((n))PP or LiPP), lithium poly-acrylic acid (Li_((n))PAA or LiPAA),lithium carboxyl methyl cellulose (Li_((n))CMC or LiCMC), lithiumalginate (Li_((n))Alg or LiAlg) and combinations thereof, with (n)denoting multiple attached Li; polyaniline or substituted polyaniline,polypyrroles or substituted polypyrroles and so forth.

Any of anode material particles 150, 150A, 150B may be coated by thinfilms (e.g., 1-50 nm, or 2-10 nm thick) of carbon (e.g., amorphouscarbon, graphite, graphene, etc.) and/or transition metal oxide(s)(e.g., Al₂O₃, B₂O₃, TiO₂, ZrO₂, MnO etc.)

In certain embodiments, borate and/or phosphate salt(s) 112A maycomprise borate salts such as lithium bis(oxalato)borate (LiBOB,LiB(C₂O₄)₂), lithium difluoro(oxalato)borate (LiFOB, LiBF₂(C₂O₄)),lithium tetraborate (LiB₄O₇), lithium bis(malonato)borate (LiBMB),lithium bis(trifluoromethanesulfonylimide) (LiTFSI), or any othercompound which may lead to formation of borate salts (B₂O₃) on anodeactive material particles 150, including in certain embodiments B₄Cnanoparticles 112.

In certain embodiments, borate and/or phosphate salt(s) 112A maycomprise phosphate salts such as lithium phosphate (LiPO₄), lithiumpyrophosphate (LiP₂O₇), lithium tripolyphosphate (LiP₃O₁₀) or any othercompound which may lead to formation of phosphate salts (P₂O₅) on anodeactive material particles 150.

Certain embodiments comprise composite anode material particles 150Bwhich may be configured as core shell particles (e.g., the shell beingprovided by any of coating(s) 104 and possible modifications presentedabove). Different configurations are illustrated schematically indifferent regions of the illustrated anode surface, yet embodiments maycomprise any combinations of these configurations as well as any extentof anode surface with any of the disclosed configurations. Anode(s) 92may then be integrated in cells 90 which may be part of lithium ionbatteries, together with corresponding cathode(s) 94, electrolyte 96 andseparator 98, as well as other battery components (e.g., currentcollectors, electrolyte additives—see below, battery pouch, contacts,and so forth).

In certain embodiments, anode 92 may comprise conductive fibers 169which may extend throughout anode 92 (illustrated, in a non-limitingmanner, only at a section of anode 92) interconnect cores 150 andinterconnected among themselves. Electronic conductivity may be enhancedby any of the following: binder and additives 102, coatings 170,conductive fibers 169, nanoparticles 112 and pre-coatings 164, which maybe in contact with electronic conductive material (e.g., fibers) 169.

Lithium ion cell 90 may comprise anode(s) 92 (in any of itsconfigurations disclosed herein) made of anode material with compositeanode material such as any of anode material particles 150, 150A, 150B,electrolyte 96 and at least cathode 94 delivering lithium ions duringcharging through cell separator 98 to anode 92. Lithium ions (Li⁺) arelithiated (to Li⁻⁰¹, indicating substantially non-charged lithium, inlithiation state) when penetrating the anode material, e.g., into anodeactive material cores 150 (possibly of core-shell particles 150B). Anyof the configurations of composite anode material and core-shellparticles 150B presented below may be used in anode 92, as particles150B are illustrated in a generic, non-limiting way. In core-shellparticle configurations 150B, the shell may be at least partly providedby coating(s) 164, and may be configured to provide a gap 167 for anodeactive material 150 to expand 168 upon lithiation. In some embodiments,gap 167 may be implemented by an elastic or plastic filling materialand/or by the flexibility of coating(s) 164 which may extend as anodeactive material cores 150 expands and thereby effective provide room forexpansion 168, indicated in FIG. 19 schematically, in a non-limitingmanner as gap 167. Examples for both types of gaps 167 are providedbelow, and may be combined, e.g., by providing small gap 167 andenabling further place for expansion by the coating flexibility.

FIGS. 20A-C provide schematic models for lithiation and de-lithiation ofthe anode material particles during operation of the battery, accordingto some embodiments of the invention. The inventors suggest, withoutbeing bound by theory, that different ranges of operation voltages 140result in lithiation of different parts of anode material particles 150.In various embodiments of anode material particle 150, lithiation may becarried out according to different spatial relations, e.g., core-shellparticles having cores that are interconnected by carbon fibers 169 (seeFIG. 19) may be lithiated inside-outwards, yet still exhibit zones oflithiation that correspond to the applied operation voltage range. FIGS.20A and 20B illustrate schematically models of core-shell particles 150and of spherical particles 150, respectively, for which lithiation maybe carried out from the center outwards (expanding core 168 into gap167) or from the periphery of the particle inwards, in FIGS. 20A and20B, respectively, as lithiation is carried out in increasing voltageranges from narrow range 140, through intermediate ranges 140A . . . Nto wide (prior art) voltage range 145. The inventors suggest thatchanging the operating voltage range may result in non-uniformdistribution of lithium ions throughout anode material particle 150,which may cause non-uniform degradation thereof.

FIG. 20C illustrates certain embodiments of operation pattern 143 (seee.g., FIG. 13) comprising one or several cycles of full voltage rangeoperation 145A, which are included intermittently in patterns 143comprising gradual increase of the voltage range—to effect occasionalredistribution of lithium ions in anode material particles 150. Forexample, without being bound to theory, narrow operation window 140 maycause more intense lithiation and de-lithiation of outer regions ofanode material particles 150, possibly degrading the correspondingregions more intensively than other regions of anode material particles150, resulting in lithium ion losses from these regions. Several cyclesof full range 145A may be performed to re-distributed Li ions from theinner parts to upper layers of anode material particles 150, to counterthe resulting degradation due to narrow voltage range operation. Forexample, sets of few (e.g., 1-3, 1-5, or 1-10) full voltage range cycles145A configured to redistribute lithium ions in anode material particlesof the battery may be introduced intermittently, within operationpattern 143 of gradually increasing voltage ranges 140, 140A . . . N.

Anode material particles 150, 150A, 150B, anodes 92 and cells 90 may beconfigured according to the disclosed principles to enable high chargingand/or discharging rates (C-rate), ranging from 3-10 C-rate, 10-100C-rate or even above 100 C, e.g., 5 C, 10 C, 15 C, 30 C, 100 C or more.It is noted that the term C-rate is a measure of charging and/ordischarging of cell/battery capacity, e.g., with 1 C denoting chargingand/or discharging the cell in an hour, and XC (e.g., 5 C, 10 C, 50 Cetc.) denoting charging and/or discharging the cell in 1/X of anhour—with respect to a given capacity of the cell.

Examples for electrolyte 96 may comprise liquid electrolytes such asethylene carbonate, diethyl carbonate, propylene carbonate, VC, FEC,EMC, DMC and combinations thereof and/or solid electrolytes such aspolymeric electrolytes such as polyethylene oxide, fluorine-containingpolymers and copolymers (e.g., polytetrafluoroethylene), andcombinations thereof. Electrolyte 96 may comprise lithium electrolytesalt(s) such as LiPF₆, LiBF₄, lithium bis(oxalato)borate, LiN(CF₃SO₂)₂,LiN(C₂F₅SO₂)₂, LiAsF₆, LiC(CF₃SO₂)₃, LiClO₄, LiTFSI, LiB(C₂O₄)₂,LiBF₂(C₂O₄)), tris(trimethylsilyl)phosphite (TMSP), and combinationsthereof.

Ionic liquid(s) may be added to electrolyte 96 as disclosed in WIPODocument No. PCT/IL2017/051358, which is incorporated herein byreference in its entirety; non-limiting examples comprise at most 20%,at most 10% or at most 5% of e.g., sulfonylimides-piperidiniumderivatives ionic liquid(s), selected to have a melting temperaturebelow 10° C., below 0° C. or below −4° C., in certain embodiments.

In certain embodiments, cathode(s) 94 may comprise materials based onlayered, spinel and/or olivine frameworks, and comprise variouscompositions, such as LCO formulations (based on LiCoO₂), NMCformulations (based on lithium nickel-manganese-cobalt), NCAformulations (based on lithium nickel cobalt aluminum oxides), LMOformulations (based on LiMn₂O₄), LMN formulations (based on lithiummanganese-nickel oxides) LFP formulations (based on LiFePO₄), lithiumrich cathodes, and/or combinations thereof.

It is explicitly noted that in certain embodiments, cathodes and anodesmay be interchanged as electrodes in the disclosed cells, and the use ofthe term anode is not limiting the scope of the invention. Any mentionof the term anode may be replaced in some embodiments with the termselectrode and/or cathode, and corresponding cell elements may beprovided in certain embodiments. For example, in cells 90 configured toprovide both fast charging and fast discharging, one or both electrodes92, 94 may be prepared according to embodiments of the disclosedinvention.

Separator(s) 98 may comprise various materials, e.g., polymers such asany of polyethylene (PE), polypropylene (PP), polyethylene terephthalate(PET), poly vinylidene fluoride (PVDF), polymer membranes such as apolyolefin, polypropylene, or polyethylene membranes. Multi-membranesmade of these materials, micro-porous films thereof, woven or non-wovenfabrics etc. may be used as separator(s) 98, as well as possiblycomposite materials including, e.g., alumina, zirconia, titania,magnesia, silica and calcium carbonate along with various polymercomponents as listed above.

It is explicitly noted that in certain embodiments, cathodes may beprepared according to disclosed embodiments, and the use of the termanode is not limiting the scope of the invention. Any mention of theterm anode may be replaced in some embodiments with the terms electrodeand/or cathode, and corresponding cell elements may be provided incertain embodiments. For example, in cells 90 configured to provide bothfast charging and fast discharging, one or both electrodes 92, 94 may beprepared according to embodiments of the disclosed invention.

Different configurations of anodes 92 are illustrated schematically indifferent regions of the illustrated anode surface, yet embodiments maycomprise any combinations of these configurations as well as any extentof anode surface with any of the disclosed configurations. Anode(s) 92may then be integrated in cells 90 which may be part of lithium ionbatteries, together with corresponding cathode(s) 94, electrolyte 96 andseparator 98, as well as other battery components (e.g., currentcollectors, electrolyte additives, battery pouch, contacts, and soforth).

Anode material particles 150, 150A, 155, anodes 92 and cells 90 may beconfigured according to the disclosed principles to enable high chargingand/or discharging rates (C-rate), ranging from 3-10 C-rate, 10-100C-rate or even above 100 C, e.g., 5 C, 10 C, 15 C, 30 C or more. It isnoted that the term C-rate is a measure of charging and/or dischargingof cell/battery capacity, e.g., with 1 C denoting charging and/ordischarging the cell in an hour, and XC (e.g., 5 C, 10 C, 50 C etc.)denoting charging and/or discharging the cell in 1/X of an hour—withrespect to a given capacity of the cell.

Examples for electrolyte 96 may comprise liquid electrolytes such asethylene carbonate, diethyl carbonate, propylene carbonate,fluoroethylene carbonate (FEC), EMC (ethyl methyl carbonate), DMC(dimethyl carbonate), VC (vinylene carbonate) and combinations thereofand/or solid electrolytes such as polymeric electrolytes such aspolyethylene oxide, fluorine-containing polymers and copolymers (e.g.,polytetrafluoroethylene), and combinations thereof. Electrolyte 96 maycomprise lithium electrolyte salt(s) such as LiPF₆, LiBF₄, lithiumbis(oxalato)borate, LiN(CF₃SO₂)₂, LiN(C₂F₅SO₂)₂, LiAsF₆, LiC(CF₃SO₂)₃,LiClO₄, LiTFSI, LiB(C₂O₄)₂, LiBF₂(C₂O₄), tris(trimethylsilyl)phosphite(TMSP) and combinations thereof. Ionic liquid(s) may be added toelectrolyte 96.

In certain embodiments, cathode(s) 94 may comprise materials based onlayered, spinel and/or olivine frameworks, and comprise variouscompositions, such as LCO formulations (based on LiCoO₂), NMCformulations (based on lithium nickel-manganese-cobalt), NCAformulations (based on lithium nickel cobalt aluminum oxides), LMOformulations (based on LiMn₂O₄), LMN formulations (based on lithiummanganese-nickel oxides) LFP formulations (based on LiFePO₄), lithiumrich cathodes, and/or combinations thereof. Separator(s) 98 may comprisevarious materials, such as polyethylene (PE), polypropylene (PP) orother appropriate materials.

In the above description, an embodiment is an example or implementationof the invention. The various appearances of “one embodiment”, “anembodiment”, “certain embodiments” or “some embodiments” do notnecessarily all refer to the same embodiments. Although various featuresof the invention may be described in the context of a single embodiment,the features may also be provided separately or in any suitablecombination. Conversely, although the invention may be described hereinin the context of separate embodiments for clarity, the invention mayalso be implemented in a single embodiment. Certain embodiments of theinvention may include features from different embodiments disclosedabove, and certain embodiments may incorporate elements from otherembodiments disclosed above. The disclosure of elements of the inventionin the context of a specific embodiment is not to be taken as limitingtheir use in the specific embodiment alone. Furthermore, it is to beunderstood that the invention can be carried out or practiced in variousways and that the invention can be implemented in certain embodimentsother than the ones outlined in the description above.

The invention is not limited to those diagrams or to the correspondingdescriptions. For example, flow need not move through each illustratedbox or state, or in exactly the same order as illustrated and described.Meanings of technical and scientific terms used herein are to becommonly understood as by one of ordinary skill in the art to which theinvention belongs, unless otherwise defined. While the invention hasbeen described with respect to a limited number of embodiments, theseshould not be construed as limitations on the scope of the invention,but rather as exemplifications of some of the preferred embodiments.Other possible variations, modifications, and applications are alsowithin the scope of the invention. Accordingly, the scope of theinvention should not be limited by what has thus far been described, butby the appended claims and their legal equivalents.

The invention claimed is:
 1. A method of preparing a fast-charging lithium ion cell, the method comprising: forming a solid-electrolyte interphase (SEI) in the anode by: performing a first formation cycle of fully charging the cell and then discharging the cell, and performing, consecutively, a plurality of charge-discharge formation cycles, in which the cell is charged to a first capacity and discharged to a second capacity, wherein the first and second capacity are between 30% and 80% of maximal cell capacity in each of said plurality of charge-discharge formation cycles.
 2. The method of claim 1, wherein the first formation cycle is carried out at 0.03 C and the consecutive plurality of charge-discharge formation cycles are carried out at 0.1 C.
 3. The method of claim 1, wherein the first formation cycle is carried out at a variable rate, starting from under 0.02 C and increasing to over 0.3 C during the first formation cycle.
 4. The method of claim 3, wherein the variable rate is determined with respect to a DC or an AC resistance of the cell.
 5. A method of preparing a fast-charging lithium ion cell, the method comprising: forming a solid-electrolyte interphase (SEI) in the anode by: performing a first formation cycle of charging the cell to between 30 and 70% of a full cell capacity and then discharging the cell, and performing, consecutively, a plurality of charge-discharge formation cycles, in which the cell is charged to 80% of the full cell capacity and then discharged, in each of said plurality of charge-discharge formation cycles.
 6. The method of claim 5, wherein the first formation cycle is carried out at 0.03 C and the consecutive plurality of charge-discharge formation cycles are carried out at 0.1 C.
 7. The method of claim 6, wherein the first formation cycle is carried out at a variable rate, starting from under 0.02 C and increasing to over 0.3 C during the first formation cycle.
 8. The method of claim 7, wherein the variable rate is determined with respect to a DC or an AC resistance of the cell.
 9. A method of preparing a fast-charging lithium ion cell for use, the method comprising: forming a solid-electrolyte interphase (SEI) in the anode by: performing at least a first formation cycle of fully charging the cell and then discharging the cell, wherein a charging current in the first formation cycle is gradually increased during the first formation cycle, from under 0.02 C to over 0.3 C.
 10. The method of claim 9, wherein a timing or rate of the gradual increase is determined with respect to a DC or an AC resistance of the cell.
 11. A method of preparing a fast-charging lithium ion cell for use, the method comprising: forming a solid-electrolyte interphase (SEI) in the anode by: performing a first formation cycle of charging the cell and then discharging the cell, and performing, consecutively, a plurality of charge-discharge formation cycles, in which the cell is charged and discharged in each of the performed consecutive formation cycles, wherein at least one of the first formation cycle and the consecutive plurality of charge-discharge formation cycles are carried out up to a state of charge (SOC) of the cell which is 80% or less of a respective cell capacity.
 12. The method of claim 11, wherein the first formation cycle is carried out at a gradually increasing rate, spanning at least a tenfold increase in charging rate during the first formation cycle. 